1. Field of the Invention
The invention relates to a connecting rod for an internal combustion engine and to an internal combustion engine.
2. Description of the Related Art
DE 10 2010 016 037 A1 and FIG. 1 herein disclose an internal combustion engine having an adjustable compression ratio. Thus, the connecting rod 10 has a big end bearing eye 11 and a small end bearing eye 12. The big end bearing eye 11 is used to attach the connecting rod 10 to a crankshaft (not shown in FIG. 1) and the small end bearing eye 12 is used to attach the connecting rod 10 to a cylinder piston (not shown in FIG. 1) of the internal combustion engine. The connecting rod 10 is assigned an eccentric adjusting device 13 with an eccentric (not shown in FIG. 1), an eccentric lever 14 and eccentric rods 15, 16. The eccentric lever 14 has a bore arranged eccentrically with respect to a center 17 of the small end bearing eye 12 and has a center 18, The bore in the eccentric lever 14 accommodates the eccentric and a bore in the eccentric accommodates a piston pin. The eccentric adjusting device 13 is used to adjust an effective connecting rod length leff. The connecting rod length should be taken to mean the distance of the center 18 of the bore in the eccentric lever 14 from a center 19 of the big end bearing eye 11. The eccentric rods 15, 16 can be moved to turn the eccentric body 14 and hence change the effective connecting rod length leff. Each eccentric rod 15, 16 is assigned a piston 20, 21 that is guided movably in a hydraulic chamber 22, 23. A hydraulic prevails in the hydraulic chambers 22, 23 and acts on the pistons 20, 21 assigned to the eccentric rods 15, 16 so that movement of the eccentric rods 15, 16 is possible or not possible, depending on the oil quantity in the hydraulic chambers.
The adjustment of the eccentric adjusting device 13 is initiated by the action of inertia forces and load forces of the internal combustion engine that act on the eccentric adjusting device 13 during an operating cycle of the internal combustion engine. During an operating cycle, the directions of action of the forces acting on the eccentric adjusting device 13 change continuously. The adjusting movement is assisted by the pistons 20, 21 acted upon by hydraulic oil, and the pistons 20, 21 act on the eccentric rods 15, 16. The pistons 20, 21 prevent return of the eccentric adjusting device 13 due to varying directions of action of force of the forces acting on the eccentric adjusting device 13. The eccentric rods 15, 16 that interact with the pistons 20, 21 are attached to the eccentric body 14 on both sides. The hydraulic chambers 22 and 23 in which the pistons 20, 21 are guided can be supplied with hydraulic oil from the big end bearing eye 11 via hydraulic oil lines 24 and 25. Check valves 26 and 27 prevent the hydraulic oil from flowing back out of the hydraulic chambers 23 and 24 into the hydraulic lines 24 and 25. A changeover valve 29 is accommodated in a bore 28 in the connecting rod 10. The switching position of the changeover valve 29 determines which of the hydraulic chambers 22 and 23 is filled with hydraulic oil and which of the hydraulic chambers 22 and 23 is emptied. The adjusting direction or turning direction of the eccentric adjusting device 13 depends thereon. In this case, the hydraulic chambers 22 and 23 are in contact via fluid lines 30 and 31, respectively, and with the bore 28 that accommodates the changeover valve 29. An actuating means 32, a spring device 33 and a control piston 34 of the changeover valve 29 are shown schematically in FIG. 1, and the operation of these components of the changeover valve 29 is already known from DE 10 2010 016 037 A1.
As explained above, the hydraulic oil that acts on the pistons 20, 21 guided in the hydraulic chambers 22, 23 is fed to the hydraulic chambers 22, 23 via hydraulic lines 24 and 25, starting from the big end bearing eye 11. The connecting rod 10 engages on the crankshaft (not shown in FIG. 1) by means of the big end bearing eye 11 in such a way that a connecting rod bearing shell 35 is arranged between the crankshaft, namely a crankshaft bearing journal thereof, and the big end bearing eye.
A connecting pin 36 extends through apertures in the eccentric lever 14 and through an aperture in the respective eccentric rod 15, 16 in the region of each of the eccentric rods 15, 16 shown in FIG. 1 to provide articulated connection of the respective eccentric rod 15, 16 to the eccentric lever 14. FIG. 2 shows a cross section through the detail II of the connecting rod 10 in FIG. 1 and thus illustrates the prior-art articulated attachment of one of the eccentric rods 16 to the eccentric lever 14 by a connecting pin 16, which, as already explained, extends through apertures (not shown) in the eccentric lever 14 and an aperture 37 in the eccentric rod 16.
As can be seen from FIG. 2, the aperture 37 in the eccentric rod 16 and that section of the connecting pin 36 that extends through the aperture 37 each have cylindrical contours according to the prior art. To ensure proper functioning of the connecting rod, it is important to ensure that an axis of the respective eccentric rod 15, 16 and the respective connecting pin 36 are at right angles or that the axis of the respective connecting pin 36 and an axis of the eccentric of the eccentric adjusting device 13 are parallel.
This cannot be achieved with the configuration of the connection of the respective eccentric rod 15, 16 to the eccentric lever 14, as shown in FIG. 2, and therefore deviations from this ideal geometrical relationship between the axis of the respective eccentric rod 15, 16 and the axis of the respective connecting pin 36 may arise. As a result, the bearing location or connection point between the respective eccentric rod 15, 16 and the eccentric lever 14 is subject to high wear. There is a requirement for a connecting rod and for an internal combustion engine having such a connecting rod that avoids the above disadvantages.
It is the object of the invention to provide a novel internal combustion engine and a novel connecting rod.